The field of the invention is cell proliferation.
Previously we have identified and studied the synthetic multivulva genes in the nematode elegans. C. elegans is well suited to developmental genetic studies because the entire cell lineage has been mapped and is essentially invariant from one animal to the next. Thus, by comparing the cell lineage of a wild-type animal to that of a mutant animal, the changes in cellular fates caused by the mutation can be determined.
A number of mutations that alter cell lineage, termed lin mutations, were obtained in genetic screens conducted by Horvitz and Sulston in the late 1970's. A subset of the mutations affected the formation of the vulva, a structure on the ventral surface of C. elegans hermaphrodites through which eggs are laid and through which sperm enters during cross-fertilization. Six vulval precursor cells have the potential to undertake a vulval cell lineage as defined by the number and pattern of cell divisions. In a wild type animal only three of these cells actually undertake vulval cell fates and these three cells generate the 22 cells that make up the adult vulva. In multivulva (Muv) animals, most or all of the six vulval precursor cells undertake vulval cell fates. In addition to the cells required for the formation of a normal vulva, these mutant animals generate an excess of cells which cause the formation of raised, vulva-like structures on the ventral surface of the animal. On the other hand, a vulvaless (Vul) phenotype results when no or too few vulval precursor cells adopt vulval cell fates.
Genetic and molecular analyses of Muv and Vul animals have defined a Ras signal transduction pathway that mediates induction of the hermaphrodite vulva. Mutant animals in which this pathway is ectopically activated can display a multivulva phenotype, whereas mutant animals that have reduced Ras pathway signalling can display a vulvaless phenotype. As in the worm, Ras pathways have been found to control cell proliferation in a range of organisms from the yeast S. cerevisiae to humans. Members of this pathway, most commonly Ras itself, have been shown to be mutated in a broad range of human cancers.
The synthetic multivulva (synMuv) genes act as negative regulators of worm signalling pathway. The first synthetic multivulva mutant was identified by Horvitz and Sulston. The two genetic loci mutated in this mutant were termed lin-8 and lin-9. Reduction-of-function mutations in both of these loci were required for a multivulva phenotype. Subsequent genetic screens identified a set of loci which fall into the same class as lin-8, termed class A genes, and genes which fall into the same class as lin-9, termed class B genes. In general, an animal with a reduction-of-function mutation in any class A gene and a reduction-of-function mutation in any class B gene will display a multivulva phenotype yet double mutant animals have wild type vulvae. Thus far four class A loci (lin-8, lin-15A, lin-38 and lin-56) and ten class B loci (lin-9, lin-15B, lin-35, lin-36, lin-37, lin-51, lin-52, lin-53, lin-54 and lin-55) have been identified genetically.
Molecular analyses of the synMuv genes have primarily dealt with the class B genes. lin-15A and lin-15B have been cloned and sequenced. Both genes encode novel protein with no known homologs in other species. lin-36 and lin-9 have also been cloned and encode novel proteins.